Many diseases associated with human aging, including cancer, cardiovascular disorders, and neurodegenerative diseases have a strong oxidative stress component, but the basic molecular mechanisms that connect aging, age-related diseases, and oxidative stress remain insufficiently understood.
Oxidative stress is the result of unregulated production of reactive oxygen species (ROS), and cellular mismanagement of oxidation-reduction chemistry can trigger subsequent oxidative damage to tissue and organs. In particular, hydrogen peroxide is a major ROS by-product in living organisms and a common marker for oxidative stress. The chemical biology of H2O2 is much more complex, however, as mounting evidence also supports a role for H2O2 as a second messenger in normal cellular signal transduction. Peroxide bursts in response to cell receptor stimulation can affect several classes of essential signaling proteins that control cell proliferation and/or cell death. Included are kinases like the mitogen-activated protein (MAP) kinase family, transcription factors such as nuclear factor [kappa]B (NF-[kappa]B), and activating protein 1 (AP-1) as well as various protein tyrosine phosphatases (PTPs), ion channels and G proteins. Despite the far-ranging consequences of H2O2 in human physiology and pathology, mechanistic details surrounding intracellular H2O2 generation, trafficking, and function remain elusive even in the simplest eukaryotic organisms.
Accordingly, interest in developing tools to study the physiological and pathological roles of H2O2 and related ROS in living systems is widespread. For example, fluorescent probes are well suited to meet the need for tools to map the spatial and temporal distribution of H2O2 within cells. Such reagents have revolutionized the study of calcium in biological systems and hold much promise for enhancing our understanding of H2O2 physiology and pathology. The major challenge for practical H2O2 sensing in biological environments is creating water-soluble systems that respond to H2O2 selectively over competing cellular ROS such as superoxide (O2-), nitric oxide (NO), and lipid peroxides. Several types of small-molecule reporters have been described for H2O2 detection. Included are dihydro derivatives of common fluorescent dyes (e.g., 2′,7′-dichlorodihydrofluorescein, DCFH, and dihydrorhodamine 123, DHR), the Amplex Red/peroxidase system, phosphine-containing fluorophores, luminescent lanthanide complexes and chromophores with ROS-cleavable protecting groups. Limitations of these and other currently available responsive probes include interfering background fluorescence from competing ROS, potential side reactions with thiols that are present in high concentrations within cells, the need for external activating enzyme, lack of membrane permeability, and/or lack of water solubility or compatibility, requiring the use of organic co-solvents. Furthermore, these tools cannot be used on fixed or paraffin-embedded tissues, precluding their use in most pathological human situations, prospectively or retrospectively.
Therefore there is a need for new reliable redox sensor for determining the redox status of a cell.